42 CIRCULATION AND GAS EXCHANGE

What are the three components of a circulatory system?

Circulatory fluid, vessels, and a heart.

What is an open circulatory system?

Hemolymph directly bathes organs.

What is a closed circulatory system?

Blood stays within vessels.

Advantage of open systems?

Uses less energy.

Advantage of closed systems?

More efficient oxygen and nutrient delivery.

What are the three main blood vessels?

Arteries, veins, capillaries.

What do arteries do?

Carry blood away from the heart.

What do veins do?

Return blood to the heart.

Where does exchange occur?

Capillary beds.

What is single circulation?

Blood passes through heart once per cycle.

What animals have single circulation?

Fish.

What is double circulation?

Blood passes through heart twice.

What are the two circuits in double circulation?

Pulmonary and systemic.

What side of the heart pumps oxygen-poor blood?

Right side.

What side pumps oxygen-rich blood?

Left side.

What is systole?

Contraction phase.

What is diastole?

Relaxation phase.

What is cardiac output?

Blood pumped per minute.

What do heart valves do?

Prevent backflow of blood.

What is the pacemaker of the heart?

SA node.

What does the AV node do?

Delays electrical signals.

What fibers cause ventricles to contract?

Purkinje fibers.

Why are capillaries thin?

To allow exchange.

Why are arteries thick and elastic?

To handle high pressure.

Why do veins have valves?

Prevent backflow.

What is systolic pressure?

Pressure during heart contraction.

What is diastolic pressure?

Pressure during relaxation.

Normal blood pressure?

120/70 mm Hg.

What is vasoconstriction?

Narrowing of vessels (raises BP).

What is vasodilation?

Widening of vessels (lowers BP).

What drives fluid out of capillaries?

Blood pressure.

What pulls fluid back in?

Osmotic pressure from proteins.

What is lymph?

Fluid leaked from capillaries.

Function of lymphatic system?

Returns fluid to blood.

What is edema?

Swelling from fluid buildup.

What is blood made of?

Plasma + cells.

Function of red blood cells?

Transport oxygen.

What protein carries oxygen?

Hemoglobin.

Function of white blood cells?

Defense.

Function of platelets?

Clotting.

What is coagulation?

Formation of a blood clot.

What is a thrombus?

Clot inside a vessel.

What is atherosclerosis?

Plaque buildup in arteries.

What causes a heart attack?

Blocked coronary arteries.

What causes a stroke?

Blocked/ruptured brain artery.

What does LDL do?

Delivers cholesterol.

What does HDL do?

Removes excess cholesterol.

What is gas exchange?

O₂ in, CO₂ out.

How does gas exchange occur?

Diffusion.

Where does gas exchange occur?

Alveoli.

Path of air to lungs?

Nose → pharynx → larynx → trachea → bronchi → bronchioles → alveoli.

What happens in alveoli?

O₂ enters blood, CO₂ leaves.

What is ventilation?

Breathing (inhalation/exhalation).

What type of breathing do mammals use?

Negative pressure breathing.

What is tidal volume?

Air per breath.

What is vital capacity?

Maximum air volume.

What controls breathing rate?

CO₂ and O₂ levels.

What brain region controls breathing?

Medulla.

How many O₂ molecules can hemoglobin carry?

Four.

Why does O₂ diffuse into blood in lungs?

Higher O₂ pressure in alveoli.

Why does O₂ leave blood in tissues?

Higher O₂ pressure in blood than tissues.

What percent of blood is CO2?

7%

How is CO₂ transported in the blood?

As bicarbonate (HCO₃⁻) in red blood cells.

What happens to CO₂ inside red blood cells?

It reacts with water → forms carbonic acid → breaks into H⁺ and HCO₃⁻.